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Effect of stator surface area on braking torque and wall heat dissipation of magnetorheological fluid retarder
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
Magnetorheological fluid (MRF) is used as the transmission medium of the hydraulic retarder. The rheological properties are regulated by changing the magnetic field to realize the accurate control of the slow braking torque magnetic field. In magnetorheological fluid retarder and under the action of magnetic field, the flow structure and performance will be changed in a short time. The apparent viscosity coefficient increases by several orders of magnitude, the fluidity deteriorates and the heat generated by the brake cannot be well transferred through the liquid circulation. And it has influence on brake torque and wall heat dissipation of retarder to change stator surface area. In this study, the relationship between the braking torque of the MRF retarder and the stator surface area of the retarder was analyzed. In addition, phase change materials were used to directly dissipate heat on the retarder surface to reduce the retarder's operating temperature and improve the stability of the retarder's braking torque. In order to study the effect of stator diameter on braking torque of MR retarder under external magnetic field, a braking torque model was established based on MRF with one-dimensional beam theory and Bingham model properties, and a heat transfer model of wall phase change material was established to analyze the relationship between heat transfer and braking torque of MR retarder. The results show that the braking torque of MRF retarder increases with the increase of retarder radius and the heat dissipation from stator wall surface is increased. The phase change material on the wall surface can well remove the heat generated by retarder, cool the retarder, and maintain the stable braking torque of retarder. Under the appropriate stator surface conditions, phase change materials are used on the wall surface of the retarder to dissipate heat, which improve the stability of braking torque of the retarder, and promote the development of magnetorheological fluid retarder to high power.